In clinical settings, the evaluation of joint stability and range of motion is for the most part based on the subjective analysis of the examining physician. Orthopedic physicians normally evaluate joint stability by conducting an examination to subjectively observe joint translation (i.e. relative displacement of bones articulated at the joint due). The amount of joint translation is evaluated by pushing or pulling on one or more of the bones articulating at the joint in a specific direction to a clinical end point, and evaluating the relative displacement of the bones at the joint by subjective physical observation. Likewise, joint range of motion is normally evaluated by bending or rotating the joint to a clinical end point, and evaluating the range of motion of the joint by subjective physical observation. In general, there are two types of range of motion examinations: active and passive.
Due to the subjective nature of joint translation and range of motion examinations, reliable and precise assessment of joint laxity and range of motion can be difficult. There has been a need in the field to provide more objective assessment of joint laxity and range of motion for patients in a variety of clinical settings. Objective information may help relatively inexperienced physicians and other practitioners confirm a diagnosis of joint instability or loss of motion. Also, real time display of objective information may in fact facilitate proper examination techniques by inexperienced physicians. Further, objective information would allow for more accurate assessments of the results of surgery designed to restore joint stability and/or range of motion. Objective information on joint stability and/or range of motion would also be useful when seeking a second opinion of a physician not present at the physical exam, as well as documenting an initial diagnosis or chronologically documenting a recovery process.
Static or dynamic radiographic methods may be used to objectively assess and document joint translation and range of motion, however, radiographic methods are impractical, especially in office settings. In addition, it is not desirable to expose patients to unnecessary radiation.